Technical Field
This invention relates to electronic devices which determine the position and/or attitude of a body, such as Global Navigation Satellite System (GNSS) attitude sensing devices, and more specifically to a short range position sensing device.
State of the Art
Global Navigation Satellite System (GNSS) devices are commonly used to determine the position and attitude of vehicles, people, animals, or other bodies. It is sometimes desirable to know the position and orientation of a first body with respect to a second body, where the first body and the second body are a relatively short distance away from each other. For example, it might be desirable to know the orientation of a bulldozer blade (first body) with respect to the bulldozer cab (second body). One way to determine the position and orientation of a first body with respect to a second nearby body is to put either a GNSS antenna or a GNSS antenna and GNSS receiver on the first body. For example, a GNSS antenna could be mounted to the bulldozer blade, and coaxial cables could run from the blade to a GNSS receiver mounted in the cab of the bulldozer. However, these RF coaxial cables have to be carefully protected from rocks, dirt, oil, etc. The cables require spring coils to remain flexible but not permit them to drop on the ground with large angle changes of the blade relative to the cab. The range of motion may be as much as 20 feet. Thus is it not desirable to run coaxial cables between the first body and the second body in many cases.
An alternative is to put both the GNSS antenna and the GNSS receiver on the bulldozer blade. But the shock and vibration of first bodies such as a bulldozer blade can be intense, and it is often not possible for the GNSS receiver to retain carrier phase lock through this shock and vibration. Thus in many situations it is not desirable to have both a GNSS antenna and the GNSS receiver on the remote first body.
Accordingly, what is needed is a device for determining the position and orientation of a first body with respect to a second body, without requiring that a GNSS antenna or a GNSS receiver be mounted to the first body.